Volume 182, 2015

Electrode kinetics of the NiO porous electrode for oxygen production in the molten carbonate electrolysis cell (MCEC)

Abstract

The performance of a molten carbonate electrolysis cell (MCEC) is to a great extent determined by the anode, i.e. the oxygen production reaction at the porous NiO electrode. In this study, stationary polarization curves for the NiO electrode were measured under varying gas compositions and temperatures. The exchange current densities were calculated numerically from the slopes at low overpotential. Positive dependency on the exchange current density was found for the partial pressure of oxygen. When the temperature was increased in the range 600–650 °C, the reaction order of oxygen decreased from 0.97 to 0.80. However, there are two different cases for the partial pressure dependency of carbon dioxide within this temperature range: positive values, 0.09–0.30, for the reaction order at lower CO2 concentration, and negative values, −0.26–0.01, with increasing CO2 content. A comparison of theoretically obtained data indicates that the oxygen-producing reaction in MCEC could be reasonably satisfied by the reverse of oxygen reduction by the oxygen mechanism I, an n = 4 electron reaction, assuming a low coverage of oxide ions at high CO2 content and an intermediate coverage for a low CO2 concentration.

Associated articles

Article information

Article type
Paper
Submitted
30 Jan 2015
Accepted
05 Feb 2015
First published
05 Feb 2015

Faraday Discuss., 2015,182, 493-509

Author version available

Electrode kinetics of the NiO porous electrode for oxygen production in the molten carbonate electrolysis cell (MCEC)

L. Hu, G. Lindbergh and C. Lagergren, Faraday Discuss., 2015, 182, 493 DOI: 10.1039/C5FD00011D

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